Introduction
Intercropping is an old agricultural practice which is growing of multiple crop species at the same time in the same place. Traditionally, intercropping has been used to increase crop production and the efficiency of the resource as well mitigate any possible risk. Intercropping has been shown to decrease the risk of crop failure by increasing the crop yield stability over time. Intercropping creates biodiversity in the cropping systems, and it is considered to make the systems more resilient against environmental perturbations, thus enhancing food security. Land equivalent ratio (LER) is often conceded as an indicator to determine the efficacy of intercropping that measure the land productivity. LER may be interpreted as the relative area required by sole crops to produce the same yields as achieved in a unit area of intercrop. The objective of the present work was to evaluatethe effect of row intercropping of three plant species such as sunflower, pumpkin and common bean on the yield, yield components and land equivalent ratio under climatic conditions of Mashhad.  
Materials and Methods
This experiment was conducted based on a randomized complete block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, Iran during two growing seasons of 2015-2016 and 2016-2016. The treatments were double (H:C, H:P, C:P) and triple (H:C:P and HH:CC:PP including one row and two rows of each species) arrangements of sunflower, pumpkin and common bean as replacement series and their sole cropping. Investigated traits were plant height, 100-seed weight, number of seeds per head, head diameter, seed weight per plant, biological yield, seed yield and harvest index of sunflower, seed weight per fruit, 100-seed weight, fresh weight of fruit, dry weight of fruit, number of seeds per fruit, dry weight of plant, biological yield, seed yield and harvest index of pumpkin and plant height, number of pods per plant, number of seeds per pods, number of branches per plant, dry weight of plant, pod weight per plant, seed weight per plant and 100-seed weight, biological yield, seed yield and harvest index of common bean. The LER was calculated as the sum of relative yields of component crops in an intercrop versus sole crops. For analysis of variance SAS ver 9.2 was used. All the means were compared according to Duncan multiple range test (p≤0.05).
Results and Discussion
The results showed that the effect of different intercropping arrangements of sunflower, pumpkin and common bean was significant (p≤0.05) on their yield components, seed yield, biological yield and harvest index. The highest seed yield of sunflower, common bean and pumpkin were observed in triple cropping as two rows (10158 kg.ha^-1), sole cropping(10493 kg.ha^-1) and common bean+ pumpkin (25014 kg.ha^-1), respectively. The maximum biological yield of sunflower, pumpkin and common bean were observed in it sole cropping, triple cropping as one row and sole cropping. The highest and the lowest land equivalent ratio were calculated with triple cropping as one row (1.69) and sunflower+ common bean (1.06), respectively.
Conclusions
Results revealed that growth, yield components and yield of sunflower, pumpkin and common bean were significantly affected by intercropping arrangements. However due to different criteria of these species associated with better use of water, radiation and nutrient resources when they are intercropped, land use efficiency was increased.
Acknowledgement
This research (40982) was funded by the Vice Chancellor for Research of Ferdowsi University of Mashhad, which is hereby acknowledged.

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